The present invention concerns a mobile telephone having a casing enclosing an electrical circuit and carrying a cover fixed to the casing in a hinged manner and incorporating a microphone.
French patent application No 96 12 305 of Oct. 9, 1996 in the name of the applicant describes a mobile telephone of the above type in which rotary contacts are incorporated into one of two hinges connecting the cover to the casing to make electrical connections between the electrical circuit and the microphone.
WO 96 21 988 describes a mobile telephone comprising a casing enclosing an electrical circuit and carrying a cover fixed to the casing in a hinged manner and incorporating a microphone, rotary contacts being incorporated into one of two hinges connecting the cover to the casing to make electrical connections between the electrical circuit and the microphone. One of the hinges between the casing and the cover comprises two contacts attached to the casing and each including a contact arm, the ends of the two contact arms bearing elastically on two conductive areas separated by an insulative material and incorporated in the part of the hinge on the cover. Thus on rotation of the cover the ends of the two contact arms trace out two circular paths on the conductive areas.
In the above implementation, the two contacts bear on the conductive tracks transversely to the rotation axis of the hinge. This arrangement cannot guarantee a uniform or adequate contact pressure between the arms and the tracks regardless of the angular position of the cover relative to the casing.
The aim of the present invention is to improve prior art mobile telephones by increasing the reliability of the electrical connection made by the rotary contacts and facilitating their manufacture on an industrial scale.
In accordance with the invention, the above mobile telephone is characterized in that the two contact arms and the two conductive areas are disposed on opposite sides of the axis of the hinge.
When the cover rotates, the two contact arms rub on the conductive areas. This rubbing has a self-cleaning effect which assures great reliability of the electrical connection.
Also, the disposition of the contact arms and the conductive areas on either side of the rotation axis of the hinge enables the contact arms to apply to the conductive areas a pressure directed towards the above axis which is divided on either side of that axis. The contact pressure is therefore regular and homogeneous regardless of the angular position of the cover relative to the casing.
The two contact arms and the two conductive areas are preferably symmetrical about the axis of the hinge.
The position of the conductive areas relative to the contact arms is such that when the cover is folded onto the casing the end of one contact arm bears on the insulative material between the two conductive areas.
Accordingly, when the cover is closed, no electrical current flows between the electrical circuit of the casing and the microphone carried by the cover.
This prevents premature wear of the battery powering the device when it is not being used.
In a preferred version of the invention, each contact is a part cut out from a sheet of metal and has three arms, one constituting the contact arm, the second one having one end nested in an insulative material block incorporated in the part of the hinge on the casing and the third arm opposite the first one having its end in contact with the electrical circuit of the casing.
This reduces the number of parts, facilitates assembly and improves reliability.
For the same reasons, the conductive areas are preferably each a part cut out from a sheet of metal, bent to shape, and fixed to an insulative material block incorporated in the hinge of the cover.
In an advantageous version of the invention, the part of the hinge on the casing has a frustoconical surface centered on the axis of the hinge in which nests a complementary frustoconical surface of the part of the hinge on the cover.
This nesting enables perfect centering of the two parts of the hinge and in particular of the contact arms relative to the conductive areas.
The other hinge between the casing and the cover preferably includes a spring pressing the aforementioned two complementary frustoconical surfaces together, a clearance being provided between the two parts of said other hinge to enable the cover to be removed by compressing the spring and disengaging the two complementary frustoconical surfaces.
It is therefore easy to demount the cover to replace it with a new cover.
In one particular version of the invention, the other hinge comprises two surfaces pressed into contact with each other by a spring, one of these surfaces comprising a plurality of raised portions which are angularly offset and engaged in recesses formed in the other surface to define a plurality of angular positions of the cover relative to the casing.
In this way the fully closed position of the cover and that at the optimum position of use can be defined accurately.
Each raised portion preferably has a summit and an up ramp and a down ramp disposed symmetrically on opposite sides of the summit.
The up and down ramps of the raised portions facilitate rotation of the cover whilst assuring accurate positioning of the cover in various preferred positions.
The two surfaces in contact preferably have three raised portions and three recesses offset relative to each other by 120xc2x0.
This angular offset by 120xc2x0 enables the cover to pivot between a closed position and a position offset by 120xc2x0 in which the microphone on the cover occupies an optimum location for using the telephone.
The two surfaces in contact can preferably be disengaged from each other.
This facilitates removing the cover to replace it with a new cover.
In an advantageous version of the invention, the raised portions and the recesses cooperate with each other to define a position in which the cover is completely folded onto the casing and the rotary contacts incorporated in the other hinge do not make the electrical connection between the electrical circuit and the microphone in the above position and as far as a first angular position of the cover and make the electrical connection when the angular position of the cover is beyond the above first position.
Other features and advantages of the invention will become apparent in the following description.
In the accompanying drawings, which are given by way of non-limiting example: